4Js Genero 2.11 COMBOX mysteries solved!

11/26/2008 Tim Ertl
Symtomb: You create a dynamic combobox but you can not use the display command to display data in that field even though the data is identical! The display command results in a blank field with no errors or warnings.

Not being sure if 4Js will document this but I have found a little curious quirk in Genero's combobox feature. The documentation all through out 4Js tends to over use the datatype "STRING". Most cases people using transactional databases try to keep things fast and STRINGs make a variable length records and lots of unusable blocks of disk space. So I use a lot of CHAR datatypes for strings. In most 4Js functions the automatic datatype conversion takes care of this difference.

Now we have a method called COMBOBOX that REQUIRES a STRING datatype! The automatic datatype conversions do not apply to the COMBOBOX method so now I need to do some non-4gl (C like) programming to change datatypes.  I did make a discovery that I am not sure 4Js will document although I have requested the documentation change today 11/26/2008. You can do everything with a CHAR datatype "IF" you add a "CLIPPED" in the additem function. Example:
call cb.additem(char-variable clipped,"")
Now you can "display by name char-variable" and it will display the data!

,,,Took us 11 Man hours to figure this one out! Not documented any where I can find.